Mass Number

Q.

The number of electrons and protons in calcium ion are respectively

1. 20, 20

2. 20, 18

3. 18, 20

4. 18, 18

Q. The mass number of an element is 41 and it has 21 neutrons in its nucleus. The electronic configuration of the element is:

1. 2, 8, 8
2. 2, 8, 8, 1
3. 2, 8, 18, 13
4. 2, 8, 8, 2

Q. Match the following elements with their respective mass numbers:
$$\begin{array}{cc}\text{Elements}& \text{Mass number}\\ \text{(a) Hydrogen}& \text{(i) 6}\\ \text{(b) Beryllium}& \text{(ii) 8}\\ \text{(c) Oxygen}& \text{(iii) 1}\\ \text{(d) Lithium}& \text{(iv) 16}\end{array}$$

1. (a) - (iii)
   (b) - (iv)
   (c) - (ii)
   (d) - (i)
2. (a) - (iii)
   (b) - (iv)
   (c) - (i)
   (d) - (ii)
3. (a) - (iii)
   (b) - (ii)
   (c) - (iv)
   (d) - (i)
4. (a) - (iii)
   (b) - (ii)
   (c) - (i)
   (d) - (iv)

Q. Determine the molecular formula of an oxide of iron in which the mass per cent of iron and oxygen are 69.9 and 30.1